Battle of Roncesvalles

The Battle of Roncesvalles was the final battle in the invasion of Moorish Spain by Charlemagne which resulted in the slaughter of his rearguard, led by the Duke of Brittany, Roland. However, the Frenk army slaughtered the Muslim army, which was led by the Emir of Babylon, the King of Spain, and the Prince of Cappadocia, and it was known for the high casualties on both sides.

Background
The Frenks invaded Spain in 778 CE, facing many Muslim armies in the north of Moorish Hispania. They besieged Saragossa, whose king Marsilla and queen Bramimonde fought hard to defend the city. However, there were no defenders left after a month, and the city fell.